January Jones, John Slattery, Elisabeth Moss and others look back on the scenes and episodes that defined their characters.

The long road to Mad Men's conclusion enters its final stretch on April 5, when Matthew Weiner's landmark AMC drama kicks off its last seven episodes.

To mark the goodbye, The Hollywood Reporter spoke with 24 key players for the March 20 cover story, a definitive oral history of the show that made basic cable prestigious and changed the way most viewers look at TV drama. Obviously, not everything made the final edit. So as the series comes to a close, here's what seven members of the cast (January Jones, John Slattery, Elisabeth Moss, among others) had to say about their biggest episodes — and some of the more absurd moments on- and offcamera that helped make them so memorable.

"Tea Leaves": Season 5, Episode 2After being M.I.A. in the premiere, Betty (Jones) re-emerges having gained a considerable amount of weight. Jones & Co. manage to keep the dramatic change in her character's appearance a secret until the night the episode airs.

Paparazzi did get one picture of me. They climbed a fence right outside of our base camp at work, as I was in the prosthetics and the weight-gain suit. After it came out, Matt had people shielding me with umbrellas everywhere I walked. It was really annoying. But nobody really put it together. I think they thought I'd just gained a lot of weight from being pregnant. It took a lot of time the first season, just getting it right — five or six hours every time we did the prosthetics. It took another hour and a half to take it off. When we first started doing it, I was very late in my pregnancy. Then we did it right after I gave birth. Being pregnant in that and having to nurse … it was so uncomfortable. I think one of my earliest call times for hair and makeup was 2:30 a.m. Then I had to sit there for six hours. But when Matt called to tell me the idea for that storyline, I just loved it. I thought it would be so shocking to the audience. I'm game for things like that, but I did not think about the logistics at the time. By the second season, I think we got it down to four hours. We never went back to pre-heavy Betty. I stopped wearing prosthetics, but I always wore some padding for the rest of the show. I think that's realistic. She's still curvy — at least curvier than I am. — January Jones

Every year we got together for a reunion party to kick off the season. Matt was having a drink and he tells me, "You're going to sing 'My Old Kentucky Home' in blackface at this country club party on Derby Day." It wasn't until I got in the car to drive home that I thought, "What the f— did he just tell me?" I remember calling Jon Hamm. I said, "Is there a way to say I don't want to do this?" Because I didn't really want to do it. But then I thought, you can't really draw the line. You can't say, "OK, I'll ride the girl in in her underwear singing cowboy songs, but I draw the line at blackface." The day comes, and we were on location in Pasadena at this big mansion doubling for this country club. We jump in the van and shoot over to the set, the van door opens and the first person I see is a very large African-American L.A. motorcycle cop. He looks at me like "What the?" He doesn't know what to make of me. And I'm like, "Hey! How you doing?" I walk right past him and then up onto this stage. I wish that they had shot the other side first or simultaneously because there were 200 extras and all our people watching as I belt through the first version of this song. There was a sea of mouths hanging open. I particularly remember Rich Sommer's [Harry Crane] face looking like, "What the hell am I watching?" — John Slattery

Nothing is off-the-cuff over there. It's very meticulously planned out. For that episode, I got a call a month before saying that they wanted me to go take Charleston lessons with Vincent. I thought, "I guess that means I'm going to be in another episode." (Laughs.) Even once the character was recurring, I didn't have a contract. Every episode of every season was just kind of episode-to-episode for me. Vinnie and I took lessons twice a week with the Dance Doctor in Santa Monica. Of course we learned very specific choreography — and then when we shot the scene at midnight or something, we kind of had to change the choreography all around because of the orientation of the dance floor and the cameras. It's one of my favorite scenes that I've ever been able to shoot in anything, and it was such a great moment for those characters, too. — Alison Brie

"The Suitcase": Season 4, Episode 7Considered by critics and fans as one of the series' standout episodes, the hour focuses almost exclusively on Don (Hamm) and Peggy (Moss) as they burn the midnight oil, working on deadline for the Samsonite account.

It was such a gift, that episode. It was so beautifully written and it came at a really great time in the series, definitely a turning point for me as far as my place in the show. It was odd in a way because it is such an ensemble atmosphere, and all the sudden it was just me and Jon for pretty much the whole time. Mark Moses [Duck Phillips] came in for the fantastic scenes that he did, but it was pretty much just the two of us. It's weird for me to say that it's my favorite episode, because I'm in it so much, but I think that it's beautiful. It's like a two-hander play. — Elisabeth Moss

"The Runaways": Season 7, Episode 5The culmination of several years of increased paranoia for the character, Michael Ginsberg (Ben Feldman) suffers a psychotic break, cuts off his own nipple and presents it to Peggy in a box. He is never seen again.

At the start of the last season, Matt would call people in and try to explain what's going to be going on with their characters. He told me everything. It was probably the most extensive macro conversation I ever had with him. Before that it was kind of, "These are your lines, learn them." If someone calls me into their office, in any situation, I immediately expect the worst. I was also constantly paranoid and scared on that show. It was the most exciting job I ever had because I was constantly scared to death every day that I showed up to work. Matt was very particular about that prosthetic nipple. Props came up with one version of it, and he wanted another. Everything you saw onscreen was always carefully thought out by him, explained and discussed to a great extent before it ended up being on the camera. It was a weird day. On one hand, you're doing something heavy. But it's also ridiculous. When the camera is on, it's this terrible serious thing. When it's off, I'm holding a bloody nipple. — Ben Feldman

"A Little Kiss": Season 5, Episode 1After being off the air for a year and a half, 'Mad Men' returns with a new leading lady for Don and a surprising musical number. Megan (Jessica Pare) coos her way through French tune "Zou Bisou Bisou" and promptly lights the Internet on fire.

Coming into my first season as a regular, as Mrs. Draper, and having to do a literal song-and-dance routine for all of these people whose work I'd admired for years … it was really stressful. I had a lot of anxiety. But I was given some really great people to work with, a great choreographer, and we worked really hard on it. We didn't have a ton of time to prepare so it was pretty intensive. I was so close to it at that time that I wasn't thinking about how people would react. I just wanted to make sure that I would hit my marks. So the reception was a surprise. It shouldn't have been. Many a more seasoned actor would have seen it coming. It was so exciting to have people talk about something I was involved in. It was a real f—ing lucky break. — Jessica Pare

"Waterloo": Season 7, Episode 7After witnessing the moon landing, Bert Cooper (Robert Morse) dies — only to return in a dream sequence to sing and dance to "The Best Things in Life Are Free" to a melancholy Don.

There was a fleeting thought that maybe people might think it was a reach, a little wild. But I soon forgot that because I trust Matt completely. The day we filmed, it was like the Super Bowl. People came out from wherever they were — the cast, the crew, my daughter was there to watch the whole number being filmed. It was quite touching. And I'll never forget Jon Hamm, how helpful he was. He stood there for eight hours as we were filming on the other side of the camera. He was rooting for this scene to be really done well, and smiled at me when a good take came. Many people would say, "Oh, I'm not going to be there all day long, put a warm body over there." But Jon was there for every moment. It was the last day of seven years for me. I'm quite pleased with how it made out. — Robert Morse